叔丁醇-水混合溶剂的混合状态对牛血清白蛋白构象的影响

应用动态光散射法测定了叔丁醇(TBA)-水混合溶剂中牛血清白蛋白(BSA)流体动力学半径, 并通过分析BSA的荧光光谱和紫外-可见光吸收光谱, 研究BSA在TBA-水混合溶剂中的构象变化. 同时, 通过分析TBA-水二元体系和BSA-TBA-水三元体系静态散射光的变化, 探讨TBA-水溶剂体系的混合状态及其对BSA在水溶液中构象变化的影响. 结果表明, TBA-水溶剂体系的混合状态与BSA的构象变化密切相关, 低浓度的混合溶剂中, 水分子在TBA周围形成疏水水化结构, 与蛋白质疏水基团的选择性结合, 破坏了蛋白质的稳定结构, 但是, 少量TBA的加入削弱了蛋白质疏水基团间的疏水相互作用, 有利于蛋白质形成更紧密的构象; 高浓度的混合溶剂中, TBA分子相互聚集形成胶束, 削弱了对蛋白质的变性作用.

Influence of the Mixing State of tert‐Butyl Alcohol‐water Mixtures on the Conformation of Bovine Serum Albumin

The hydrodynamic radii of bovine serum albumin (BSA) in TBA‐water mixtures were determined by dynamic light scattering measurements and utilized to investigate the conformational change of BSA in TBA‐water mixtures, together with the analysis of the fluorescence spectra and UV‐vis absorption spectra of BSA. Meanwhile, static light scattering measurements were used to probe the mixing state of the binary mixtures of TBA‐water and the ternary mixtures of BSA‐TBA‐water and its influence on the conformation of the protein. A close relationship between the mixing state of TBA‐water mixtures and the conformation of BSA was observed. The mixing state of TBA‐water mixture at a low concentration was characterized by the clathrate hydrate of TBA caged by water molecules and it was found that hydrophobic binding of TBA to nonpolar groups of BSA in general destabilized the native structure of the protein, however, addition of a small amount of TBA attenuated the hydrophobic interactions among nonpolar groups of the protein and promoted a more ordered conformation. The results clearly showed that clustering of TBA at a high concentration reduced the effectiveness on destabilization of the compact conformation of proteins.